Replies

1. 
   Jon_R | Jul 16, 2019 09:10pm | #1

   There is little value to insulation put between steel framing (even more so with a steel pan attached to the underside). So build everything above the frame.

   Here is some info about exterior perms (if you don't ventilate the pan) and how it effects a design. But trapped moisture (eg, between floor and pan) isn't good for wood or steel.

   If you want to apply rigid foam directly to a steel frame, you may be able to use round squash blocks to avoid foam compression without adding much thermal bridging.

   From recent experience: the time to take additional action against a trailer frame rusting is when it is new and open.

2. GBA Editor
   Martin Holladay | Jul 17, 2019 05:32am | #2

   Jayne,
   You don't need to drill holes in the steel pan. Adding a continuous layer of rigid foam above the steel pan is a good idea. Skip the mineral wool, however -- just add whatever thickness of rigid foam you need to achieve your R-value goal, followed by a layer of OSB subflooring. You can attach the OSB to the steel pan with long screws.

3. 
   Jayne_Torres | Jul 17, 2019 09:46am | #3

   Thanks to you both. Jon, that info about exterior perms is invaluable!

   I'll go with the rigid foam. Martin...why OSB instead of Advantech?

   Thank you!!

1. GBA Editor
   Martin Holladay | Jul 18, 2019 05:14am | #5

   Jayne,
   As Tim explains below, Advantech is a brand of OSB -- so the OSB was your suggestion, not mine. Many builders (including me) might prefer to use plywood. Either will work.

4. 
   user-6184358 | Jul 17, 2019 08:39pm | #4

   Advantech is a brand name OSB